1. Field of the Invention
The present invention relates to a method for the manufacture of an elastic roll having a hard roll core including in particular of metal and an elastic covering layer, wherein, to form the elastic covering layer, a fiber bundle including of a plurality of fibers is wound onto the roll core to form fiber layers lying on top of one another, with the direction of winding of the fibers being essentially parallel to one another and at an angle to the peripheral direction of the roll core. The invention is further directed to a roll, in particular for the smoothing of paper webs, having a hard roll core including in particular of metal and being provided on its outside with an elastic covering layer which comprises a plurality of fiber layers lying radially on top of one another and comprising of a soft matrix material with fibers embedded therein.
2. Discussion of Background Information
Elastic rolls of this kind are used, for example, in the satining of paper webs. Here, one elastic roll forms, in each case together with a hard roll, a press gap through which the paper web to be treated is guided. While the hard roll has a very smooth surface including, for example, of steel or chilled cast iron and is responsible for the smoothing of that side of the paper web facing it, the elastic roll acting on the opposite side of the paper web effects a homogenizing and compacting of the paper web in the nip. The order of magnitude of the rolls ranges from lengths of about 3 to 12 m and diameters from about 450 to 1500 mm. They can withstand line forces of up to about 600 N/mm and compressive stresses of up about to 130 N/mm2.
As the trend in paper manufacturing is towards performing satining in an online operation, i.e. towards guiding the paper web exiting the paper machine or coating machine directly through the paper smoothing apparatus (calender), higher demands than previously are made on the rolls of the smoothing apparatus, particularly on the elastic covering layers of the rolls. As a result of the high transportation speeds of the paper web required in online operation and the high rotation speeds of the calender rolls associated with this, nip frequencies, that is the frequencies with which the covering is compressed and relieved of its load again, are achieved, which lead to resonances in the roll jacket or in the rolls.
These resonances lead to vibrations of the calender rolls which lead to transverse stripes perpendicular to the production direction, so-called xe2x80x9cbarringsxe2x80x9d in the surface of the elastic covering of the rolls after a certain running time. These transverse stripes can typically have a width of about 3 to 10 mm in the peripheral direction and a spacing of about 5 to 10 mm.
The vibrations are caused by irregularities which can be caused, for example, by an uneven breast box, irregularities in the roll drive or by other irregularities in the running of the roll. The transverse stripes in the covering layer can occur both due to plastic deformation of the matrix material and to irregular wear. These transverse stripes in the covering layer finally lead to corresponding pressure marks on the calendered paper web so that the quality of the paper web is not sufficient.
The transverse stripes in the covering layer of the roll have to be eliminated by grinding the covering layer which results in a much lower service life of the roll coverings.
It is an aspect of the invention to provide a method for the manufacture of an elastic roll and to provide such an elastic roll where the occurrence of barrings is avoided.
The part of the aspect relating to the method is satisfied in accordance with the invention, starting from a method of the kind initially mentioned, by at least two fiber layers lying on top of one another being wound alternately in an identical but opposite manner to form a cross-composite layer, i.e. by the angular positions relative to the longitudinal axis of the roll of the fiber bundles of two fiber layers wound in an identical but opposite manner being symmetrical to the cross-sectional surface of the roll, by a damping fiber layer with fiber bundles being wound onto the cross-composite layer, with the angular position of this fiber bundle being substantially flatter than the angular positions of the fiber bundles of the cross-composite layer and by a cross-composite layer again being wound onto the damping fiber layer.
A roll made in accordance with the invention is characterized by the fibers of the fiber layers each, extending at an angle to the longitudinal axis and essentially parallel to one another, by at least two fiber layers lying on top of one another forming in each case a cross-composite layer, with the fibers of the individual fiber layers each extending alternately in an identical but opposite manner, i.e. by the angular positions of the fibers relative to the longitudinal axis of the roll being symmetrical to the cross-sectional surface of the roll, by the covering layer including at least two cross-composite layers, and by a damping fiber layer with fibers of a uniform angular position being provided between the cross-composite layers, with the angular position of these fibers being substantially flatter than the angular positions of the fibers of the cross-composite layers.
The occurrence of barrings is therefore avoided in accordance with the invention by a special winding technique. The rolls manufactured using the winding technique in accordance with the invention have the property of a vibration of the roll being avoided by special damping fiber layers inside the covering layer. While the cross-composite layers including in each case fiber layers wound in an identical but opposite manner have a relatively low E modulus, the damping fiber layers wound in each case in a uniform angular position have a very high stiffness, with pressure forces acting on the covering layer being transferred to the covering layer as torsion due to the very flat angular position of the fiber bundles. In this way, when pressure is applied, minimum torsion of the covering layer occurs, whereby vibrations in the covering layer and so the occurrence of barrings is avoided. The impacts which occur during operation due, for example, to irregularities in the breast box or to irregularities in the drive, are thus taken up by the specially designed damping fiber layers.
In accordance with an advantageous embodiment of the invention, the fiber bundle is wound onto the roll core in a multi-layer design with an essentially uniform angular position to form in each case one of the fiber layers of the cross-composite layers. The fiber layers of the cross-composite layers are thus made in a multi-layer design in each case, i.e. they comprise in each case several layers of fibers of an essentially uniform angular position wound over one another. The required thickness and so the required elasticity of the covering layer is achieved in this way.
At least two or more of these preferably multi-layer fiber layers having a uniform angular position are then put together to form one cross-composite layer in each case. A high stiffness of the covering layer is achieved due to the winding of the individual fiber layers within one cross-composite layer in an identical but opposite manner.
The fiber bundle is preferably wound onto the roll core in one layer to form the damping fiber layer. The damping fiber layers are in this way made substantially thinner than the cross-composite layers so that the stiffness of the covering layer is not disadvantageously reduced. Nevertheless, when pressure is exerted, it is achieved by the thin damping fiber layers, which are not wound in a cross-composite, but in a uniform angular position, that the vibrations in the covering layer and so the occurrence of barrings are avoided.
Within the meaning of the present invention, one-layer defines that when the damping fiber layer is wound, the fiber bundle is wound onto the roll core until the cross-composite layer underneath it is fully covered. The fiber bundle can subsequently, for example, be cut off at the roll end.
In accordance with another advantageous embodiment of the invention, several cross-composite layers and damping fiber layers are wound on top of one another, with each cross-composite layer being followed by a damping fiber layer. Generally, a plurality of corresponding layers can be provided, with a cross-composite layer preferably being wound as the radially outermost layer.
Particularly when the fiber bundles of two damping fiber layers following one another are wound in identical but opposite manners, the covering layer has optimum damping properties since the relevant torsion of the two damping fiber layers following one another is in each case directed in the opposing direction so that the torsion forces which occur cancel each other out over the whole covering layer. The surface of the elastic covering layer remains free of torsion in this way.
The damping fiber layers are advantageously wound with a substantially smaller radial thickness than the cross-composite layers. The damping fiber layers in this way have a very high E modulus, whereby the translation of the radial impacts acting on the covering layer into a torsional movement is further improved.
In accordance with another preferred embodiment of the invention, radially outer cross-composite layers are wound with a steeper angular position than radially inner cross-composite layers. An optimum thermal expansion behavior of the roll in accordance with the invention is achieved by these outwardly increasing angular positions. A radially inner cross-composite layer with an angular position of about xc2x145xc2x0, a damping fiber layer following thereon with an angular position of about +8xc2x0, a further cross-composite layer with an angular position of about xc2x165xc2x0, another damping fiber layer with about xe2x88x928xc2x0 and, finally, a further cross-composite layer with an angular position of about xc2x175xc2x0 can, for example, be wound, with the damping fiber layers preferably being wound substantially thinner than the cross-composite layers.
In accordance with another advantageous embodiment of the invention, a radially inner connecting layer is first applied to the roll core and subsequently a radially outer functional layer applied to the connecting layer to form the covering layer. The physical properties of the two layers required in each case can be ideally set by a separation into a connecting layer and functional layer. For example, the outer functional layer should conventionally have high elasticity, while the inner connecting layer should have high stiffness. To improve the thermal conductivity of the covering layer and so the dissipation of unwanted heat from the covering layer, fiber materials are used which have a higher conductivity than the matrix material used. In addition, fillers can be embedded in the elastic material which also have a higher thermal conductivity than the matrix material.
The fibers are preferably surrounded with a soft matrix material, in particular a resin/hardener combination, prior to the winding on the roll core to manufacture the roll. This can be done, for example, by the fibers being drawn through a resin/hardener bath. The fibers can, however, generally be wound onto the roll core in an essentially dry condition and be subjected to a soft matrix material, in particular to a resin/hardener combination, and in particular be fully embedded in the matrix material, during or after winding.
The fiber layers can be formed by winding single fibers, fiber bundles or fiber rovings, with a fiber layer being able to be wound within the meaning of the present invention both as one layer, i.e. wound singly, and in multiple layers, i.e. wound several times.
According to an aspect of the present invention, a method for manufacturing an elastic roll is provided including winding at least one fiber bundle comprising of a plurality of fibers to form fiber layers onto a hardroll core. The fiber layers being formed to lie on top of one another, with a direction of winding of the fibers being essentially parallel to one another and at an angle to a peripheral direction of the roll core. Wherein fiber layers lying on top of one another are wound alternately in an identical but opposite manner to form a cross-composite layer. Furthermore, the invention includes winding a damping fiber layer with fiber bundles of a uniform angular position onto the cross-composite layer, with an angular position of these fiber bundles being substantially flatter, relative to a longitudinal axis of the roll, than the angular positions of the fiber bundles of the cross-composite layer; and winding another cross-composite layer again onto the damping fiber layer.
According to another aspect of the present invention, the hard roll comprises metal. Additionally, other aspects of the present invention include wherein angular positions relative to a longitudinal axis of the roll of the fiber bundles of two fiber layers wound in an identical but opposite manner are symmetrical to a cross-sectional surface of the roll.
In another aspect of the present invention, the fiber bundle is wound onto the roll core in multiple layers with an essentially uniform angular position to form in each case one of the fiber layers of the cross-composite layers. According to a further aspect of the present invention, the fiber bundle is wound onto the roll core in one layer to form the damping fiber layer. In another aspect of the present invention, different cross-composite layers are wound with angular positions differing in magnitude.
According to a still further aspect of the present invention, several cross-composite layers and damping fiber layers are wound over one another, with each cross-composite layer being followed by a damping fiber layer. Further aspects of the invention include wherein a cross-composite layer is wound as the radially outermost layer. According to other aspects of the present invention, the fiber bundles of two damping fiber layers following one another are wound in an identical but opposite manner.
According to another aspect of the present invention, the damping fiber layers are wound with an essentially smaller radial thickness than the cross-composite layers. According to a further aspect of the present invention, radially outer cross-composite layers are wound with a steeper angular position than radially inner cross-composite layers. According to a still further aspect of the invention, the cross-composite layers are wound with angular positions of approximately xc2x140xc2x0 to approximately xc2x180xc2x0.
According to an aspect of the present invention, the damping fiber layers are wound with an angular position of approximately 3xc2x0 to approximately 12xc2x0 or from approximately xe2x88x923xc2x0 to approximately xe2x88x9212xc2x0. According to another aspect of the present invention, the damping fiber layers are wound with an angular position of approximately 8xc2x0 or of approximately xe2x88x928xc2x0. Additionally, other aspects of the present invention are provided including wherein the damping fiber layers are wound with angular positions essentially equal in amount.
In another aspect of the present invention, a radially inner connecting layer is first applied to the roll core and subsequently a radially outer functional layer is applied to the connecting layer to form an elastic covering layer. According to a further aspect of the present invention, cross-composite layers and damping fiber layers are wound onto the roll core to form at least one of a connecting layer and functional layer. In another aspect of the present invention, at least one of carbon and metal and glass and aramide fibers or mixtures of these fiber materials are used as fibers.
According to a still further aspect of the present invention, the fiber bundles are formed by fiber rovings with one roving comprising in each case a plurality of fibers of the same kind lying next to one another. In another aspect of the present invention, the fibers are surrounded by a soft matrix material. According to a still further aspect of the present invention, the soft matrix material is a resin and hardener combination.
Further aspects of the invention include wherein the soft matrix material is drawn through a resin and hardener bath, prior to winding onto the roll core. According to other aspects of the present invention, the fibers are wound onto the roll core in an essentially dry condition and are exposed to a soft matrix material and completely embedded in the matrix material, during or after winding onto the roll core. According to another aspect of the present invention the soft material matrix is a resin and hardener combination.
According to a further aspect of the present invention, a roll is provided having a hard roll core and an elastic covering layer on the outside of the core, the elastic covering including a plurality of fiber layers lying radially on top of one another, including a soft matrix material with fibers embedded therein. Fibers of the fiber layers each extend at an angle to a longitudinal axis of the roll core and essentially parallel to one another. At least two fiber layers lying on top of one another form in each case a cross-composite layer, with the fibers of the individual fiber layers each extending alternately in an identical but opposite manner. The covering layer including at least two cross-composite layers. A damping fiber layer with fibers of a uniform angular position is provided between the cross-composite layers, with angular position of these fibers being substantially flatter than angular positions of the fibers of the cross-composite layers.
According to a further aspect of the present invention, the roll is used for smoothing paper webs. According to a still further aspect of the invention, the roll core comprises metal. According to an aspect of the present invention, angular positions of the fibers relative to the longitudinal axis of the roll core are symmetrical to a cross-sectional surface of the roll.
According to an aspect of the present invention, the fiber layers of the cross-composite layers are each formed in multiple layers. According to another aspect of the present invention, the fiber layers of the cross-composite layers comprise in each case several layers of fibers wound on top of one another, with fibers of one fiber layer each having an essentially uniform angular position. In another aspect of the present invention, the damping fiber layer is made in one layer. According to a further aspect of the present invention, angular positions of the fibers are different in magnitude for different cross-composite layers.
According to a still further aspect of the present invention, the covering layer comprises at least two cross-composite layers and at least two damping fiber layers. In another aspect of the present invention, the covering layer comprises three cross-composite layers. In another aspect of the present invention, the outside of the covering layer is formed by a cross-composite layer. According to a further aspect of the present invention, the fibers of two damping fiber layers following, one another are wound in an identical but opposite manner.
In another aspect of the present invention, the radial thickness of the damping fiber layers is substantially smaller than the radial thickness of the cross-composite layers. Further aspects of the present invention include wherein the damping fiber layers have a radial thickness of approximately 0.1 mm to approximately 1 mm. According to an aspect of the present invention, the damping fiber layers have a radial thickness of approximately 0.25 mm to approximately 0.6 mm. According to another aspect of the present invention, the cross-composite layers have a radial thickness of approximately 1.5 mm to approximately 3 mm. In another aspect of the present invention, the cross-composite layers have a radial thickness of approximately 2 mm.
According to a still further aspect of the present invention, the angular positions of the fibers of radially outer cross-composite layers are steeper than the angular positions of the fibers of radially inner cross-composite layers. Further aspects of the invention include wherein the angular positions of the cross-composite layers are approximately xc2x140xc2x0 to approximately xc2x180xc2x0. Further aspects of the invention include wherein the angular positions of the damping fiber layers are approximately 3xc2x0 to 12xc2x0 or approximately xe2x88x923xc2x0 to xe2x88x9212xc2x0.
According to other aspects of the present invention, the angular positions of the damping fiber layers are approximately 8xc2x0 or xe2x88x928xc2x0. According to another aspect of the present invention, the angular positions of the damping fiber layers are essentially equal in amount. According to an aspect of the present invention, the covering layer comprises a radially outer functional layer and a radially inner connecting layer to connect the functional layer to the roll core. According to another aspect of the present invention, at least one of the connecting layer and functional layer comprise cross-composite layers and damping fiber layers.
Additionally, other aspects of the present invention include the matrix material being plastic. In another aspect of the present invention, the matrix material is a plastic one of a thermosetting plastic or a thermoplastic. According to a still further aspect of the present invention, the matrix material comprises a resin and hardener combination. Further aspects of the invention include wherein the fibers are combined to fiber bundles or fiber rovings, with one roving in each case comprising a number of fibers of the same kind lying next to one another.
According to other aspects of the present invention, the fibers are made as at least one of glass, carbon, metal and aramide fibers or of mixtures of these fiber materials. Further aspects of the invention include the fiber content of the connecting layer is approximately 40 to 70 vol. %. According to another aspect of the present, the fiber content of the connecting layer is approximately 50 to 60 vol. %. According to a still further aspect of the invention, the fiber content of the functional layer is approximately 5 to 30 vol. %.
According to an aspect of the present invention, the fiber content of the functional layer is approximately 8 to 20 vol. %. According to another aspect of the present invention, the fibers of at least one of said functional layer and the connecting layer have higher thermal conductivity than the matrix material in which they are embedded.
Additionally, other aspects of the present invention are provided including a roll having a hard roll core and an elastic covering layer on the outside of said core, the method for manufacturing the elastic covering layer, including forming the elastic covering layer by winding onto the roll core at least one fiber bundle including of a plurality of fibers to form fiber layers lying on top of one another, with a direction of winding of the fibers being essentially parallel to one another and at an angle to a peripheral direction of the roll core. At least two fiber layers lying on top of one another are wound alternately in an identical but opposite manner to form a cross-composite layer; winding a damping fiber layer with fiber bundles of a uniform angular position onto the cross-composite layer, with an angular position of these fiber bundles being substantially flatter than the angular positions of the fiber bundles of the cross-composite layer. And, winding a cross-composite layer again onto the damping fiber layer, the elastic covering layer including a plurality of fiber layers lying radially on top of one another; and a soft matrix material with fibers embedded therein; wherein fibers of the fiber layers each extend at an angle to a longitudinal axis of the roll core and essentially parallel to one another. At least two fiber layers lying on top of one another form in each case a cross-composite layer, with the fibers of the individual fiber layers each extending alternately in an identical but opposite manner, wherein the covering layer comprises at least two cross-composite layers. A damping fiber layer with fibers of a uniform angular position is provided between the cross-composite layers, with angular position of these fibers being substantially flatter than angular positions of the fibers of the cross-composite layers.